Known direct steam injection (DSI) technologies for heating bitumen froth streams have a number of inefficiencies, challenges and drawbacks. For instance, various DSI techniques are prone to steam hammer vibration due the collapsing of large steam bubbles. This kind of operational limitation restricts control on bitumen froth temperatures feeding downstream froth treatment processes.
Two known techniques for heating bitumen froth are the following: (i) in-line bitumen froth steam heating system comprising direct steam injectors and static mixing devices, which is described in Canadian patent No. 2,455,011 and (ii) froth heating tower heating with shed trays to contact bitumen froth with steam for heating and deaerating the bitumen froth, which is described in Canadian patent No. 1,072,474.
These known and conventional techniques have several limitations. For instance, the DSI-static mixer technique can have an operating envelop that is more limited than is sometimes desired. The steam pressure to the DSI is externally controlled. At low pressures, steam flows into the bitumen froth as unstable jets or bubbles which can collapse and thus create vibration. The high condensing rate of steam into bitumen froth in which water content aids transfer means the effectiveness of the static mixer in limiting vibration has given limitations. In addition, the heated bitumen froth may be discharged into a holding tank with a recycle pump to aid maintenance of froth temperatures, but there may be challenges regarding heating limitations of approach temperatures. In relation to the other bitumen froth heating technique, froth heating towers are large structures relative to DSI and while units can achieve high steam efficiencies with multi-stages of sheds, which force column to have high H/D ratio, at high design froth flows turndown to average or lower result in reduced steam efficiencies. Furthermore, due to elevation these froth heating structures are generally more favorably provided with separation cells to permit gravity froth flow to the heater. In addition to achieve high froth temperatures, vessels may need to be operated under pressure to keep efficiency high.
In summary, known practices and techniques for bitumen froth heating experience various drawbacks and inefficiencies, and there is indeed a need for a technology that overcomes at least some of those drawbacks and inefficiencies.